This invention relates to a fluid flowmeter of the variable orifice-type. More particularly, this invention relates to an improved flowmeter for measuring the quantitative flow of fluids such as gases passing therethrough which is characterized by a piston-like float member which closely fits in a float guide to eliminate undesirable oscillations and cooperates with a shock absorbing chamber in the form of a sealed sight glass above the piston-like float for compensating for rapid upward and downward movement of the float.
Orifice-type fluid flowmeters are well-known in the art. Meters of this type operate on the principal of measuring the pressure drop across a restrictive orifice placed in the flow line. Such meters may use a fixed size orifice, such as a hole in a plate, in which case there is a pressure drop of the fluid from a point in front of the plate to a point behind the orifice. This pressure drop is a function of the flow.
It is also known to construct orifice flowmeters with a variable orifice and a constant pressure drop. In such meters the size of the orifice is a function of the flow. Such variable orifice-type meters have been constructed with a tapered tube, in which a fixed size "float" such as a spherical ball is placed. The float is urged upstream in the tapered tube by a predetermined force. The inside diameter of the tube tapers in such a direction as to be larger downstream. Normally, meters of the variable orifice type are made so as to function in a vertical position with the direction of flow upwards through the tube thereby relying on the force of gravity to urge the float downward.
Another type of variable orifice flow meters are those using a tube with a constant diameter and a vertical fluid escape slot or row of holes. These tubes are used with an elongated float which slides up and down inside the constant diameter tube. U.S. Pat. No. 341,841 to Gleason of May 11, 1886, and U.S. Pat. No. 1,238,498 to Dawley of Aug. 28, 1917, describe flowmeters of this general type.
Fluid flowmeters of the type referred to above and exemplified in the Gleason and Dawley patents have not been entirely successful from a commercial standpoint for several reasons. One is that the elongated float member is susceptible to oscillation due to the action of a fluid, such as a gas, passing through the meter. This makes an accurate reading of the meter difficult and in instances where precise metering is required, this operates as a serious drawback.
Another problem encountered is the rapid upward movement of the indicator member due to a surge of in-flowing gas. This can cause uncontrolled rapid upward movement of the indicator resulting in damage to the meter itself and loss of calibration. Uncontrolled downward movement of the indicator when the gas flow stops can have similar undesirable effects.
The present invention overcomes drawbacks encountered with prior flowmeters by providing an improved construction which eliminates oscillation and provides shock absorption means for accommodating and compensating for rapid upward and downward movement of a float member.